This invention relates to a justification authenticating system, a personal certificate issuing system, and a personal certificate used in these systems.
In general, personal certificates that include authentic images (of a card type or a book type), such as a credit card, cash card, membership card, student identification card, employee ID card, passport, health insurance card, and license, have been widely used. In this specification, the “authentic image” signifies an image by which an individual is identified, such as a photographic image of a face, an image of a fingerprint, or an image of a pupil.
However, incidents are so frequently occurring in which a person who is not the owner of these personal certificates substitutes another authentic image for an authentic image of the owner, and thereby the person unjustly impersonates the true owner. This is a social problem.
As a countermeasure against such counterfeiting, a technique for embedding a digital watermark into a facial photograph has been proposed (see Japanese Unexamined Patent Publication No. Hei-10-275203), the disclosure of which is herein included by reference. According to the digital watermark method, desired data is embedded into an authentic image, which is digital data, as watermark information so as to be indistinguishable to the eye, while permitting normal viewing of the authentic image.
In this technique, the justification of a personal certificate is judged in such a way that a digital watermark embedded in the personal certificate is accurately extracted by the aid of authentication equipment (for example, a card reader).
Here, it is supposed that, when a personal certificate is generally formed, the identifier of the owner of the certificate is “BBB”, and information to be added is “AAA”, and the digital watermark of “ABABAB” is embedded.
In this case, the digital watermark is read from an authentic image when authenticated. If reading fail, the identification is judged to be unjustifiable. Even if the reading is successful, according to an opposite procedure to the procedure followed when embedded, as a result of excluding the identifier “BBB” from the “ABABAB”, the information “AAA” is separated. A judgment is then made as to whether or not the information is correct. As a result, if information is correct, it is judged to be justifiable, and, if not correct, it is judged to be unjustifiable.
However, the above technique is at a disadvantage in that, since the justification is determined only by the data stored on the card, falsification is easily perpetrated if the algorithm for embedding a digital watermark is leaked or revealed. For example, the illegality of an offender B cannot be exposed even if the offender B who stole the credit card of a person A merely pastes a facial photograph in which a digital watermark according to this algorithm is embedded on the facial photograph of the offender B, and the offender B shops with this credit card. Accordingly, the above technique cannot completely avoid problems about security.